Removing duplicate objects with Underscore for Javascript
.uniq/.unique accepts a callback
var list = [{a:1,b:5},{a:1,c:5},{a:2},{a:3},{a:4},{a:3},{a:2}];var uniqueList = _.uniq(list, function(item, key, a) { return item.a;});// uniqueList = [Object {a=1, b=5}, Object {a=2}, Object {a=3}, Object {a=4}]Notes:
- Callback return value used for comparison
- First comparison object with unique return value used as unique
- underscorejs.org demonstrates no callback usage
- lodash.com shows usage
Another example : using the callback to extract car makes, colors from a list
If you're looking to remove duplicates based on an id you could do something like this:
var res = [ {id: 1, content: 'heeey'}, {id: 2, content: 'woah'}, {id: 1, content:'foo'}, {id: 1, content: 'heeey'},];var uniques = _.map(_.groupBy(res,function(doc){ return doc.id;}),function(grouped){ return grouped[0];});//uniques//[{id: 1, content: 'heeey'},{id: 2, content: 'woah'}]
Implementation of Shiplu's answer.
var foo = [ { "a" : "1" }, { "b" : "2" }, { "a" : "1" } ];var x = _.uniq( _.collect( foo, function( x ){ return JSON.stringify( x );}));console.log( x ); // returns [ { "a" : "1" }, { "b" : "2" } ]